Permeable pressure sensitive adhesive

ABSTRACT

The present invention relates to a pressure sensitive, hot melt processable adhesive composition comprising a polar plasticising oil and a polar polyethylene copolymer, and a layered adhesive construct and a medical device comprising the adhesive composition according to the invention.

This is a national stage of PCT/DK08/050146 filed Jun. 17, 2008 andpublished in English, which has a priority of Denmark no. PA 2007 01003filed Jul. 6, 2007, hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a pressure sensitive, hot meltprocessable adhesive composition comprising polar plasticising oil and apolar polyethylene copolymer, and a layered adhesive construction and amedical device comprising the adhesive composition according to theinvention.

BACKGROUND OF THE INVENTION

Pressure sensitive adhesives have for a long time been used forattaching medical devices, such as ostomy appliances, dressings(including wound dressings), wound drainage bandages, devices forcollecting urine, orthoses and prostheses to the skin.

Hydrocolloid adhesives containing hydrophilic particles or absorbents,which absorb moisture into the adhesive bulk and transmit moisture whenconditions are saturated, are one well-known group of pressure sensitiveadhesives useful for attaching medical devices to the skin. However, theretention of moisture in hydrocolloid adhesives may cause changes in theadhesive, such as swelling, loss of cohesion and disintegration.Non-absorbing adhesives on the other hand, may trap excessive moisturebetween the skin and adhesive, causing weakening of adhesion andmaceration of the skin.

Due to the delicate nature of skin, there is a narrow window where apressure sensitive adhesive can function as a good and skin friendlyadhesive: On one hand, the adhesive should be able to attach the medicaldevice to the skin and the device should not fall of during wear and onthe other hand, removal of the medical device from the skin should notcause damage to the skin.

For medical uses, a high water vapour transmission through the pressuresensitive adhesive is desirable. However, the availability of pressuresensitive adhesives with high water vapour transmission, which aresuitable for skin contact use, is limited.

The water vapour transmitting pressure sensitive adhesives currentlyused for adhesion to the skin are mainly silicone, PU and acrylic basedadhesives.

Pressure sensitive adhesives based on acrylics are usually solvent basedand may include toxic residues and monomers causing malodour. Theseadhesives may incorporate hydrophilic components, such as hydrocolloids,which absorb moisture. However, the content of hydrophilic componentsand hence the absorption of moisture changes the properties of theadhesive, swelling and reduced adhesion being the most undesirableeffects. The wear time of such acrylic adhesives is typically short dueto these effects.

Silicone adhesives are relatively expensive and have a relatively lowmoisture transmission, which causes problems with regard tobreathability. Adhesion may also be compromised, when moisture builds upbetween the skin and the adhesive. Moreover, the compatibility ofsilicones with other organic materials (e.g. polymers) is limited, whichaffects the blending stability with performance enhancing additives, andadhesion to reinforcement materials of another chemical composition.

Pressure sensitive adhesives based on silicone or polyurethane aretypically thermoset materials that undergo an irreversible cross-linkingreaction during processing.

Adhesives based on apolar polymers like SIS and PIB are well known inthe technical field of medical adhesives. E.g. WO 99/11302 describingadhesives for medical use based on SIS, PIB and hydrocolloids and U.S.Pat. No. 4,551,490 describing adhesives containing SIS/SI, PIB/butylrubber, tackifier, mineral oil and hydrocolloids.

Ethylene copolymers are often used in hot-melt adhesives for e.g.packaging and labels. The EVAs used for these purposes are thetraditional EVA types containing up to 40% vinyl acetate, i.e. thepolymer is relatively apolar.

Adhesives containing EVA with more than 40% vinyl acetate are alsodescribed.

U.S. Pat. No. 4,477,325 describes a skin barrier composition made ofEVA, PIB and water absorbing particles or polymers. The EVA may containfrom 25 to 65% by weight of vinyl acetate.

U.S. Pat. No. 6,933,342 describes a formulation comprising a triblockcopolymer (styrene-diene-styrene), a terpene resin, a liquid and EVApolymer wherein the EVA polymer preferably possess a vinyl acetatecontent of more than 50% by weight.

U.S. Pat. No. 6,225,520 describes an adhesive containing ethylenecopolymer as e.g. EVA, solid tackifier resin, liquid tackifier resin,antioxidant and optionally a diluent. The EVA polymer exhibiting a vinylacetate content of between 15 and 65% by weight. The invention relatesto adhesives for labels and tapes, including tapes for skin contact.

The adhesive described above all have the drawback that they containapolar components, which result in an adhesive matrix (adhesive withouthydrocolloids) with no or low water permeability. If the adhesive has tobe used for skin contact, they need to be able to handle moisture. Whenthe types of materials described above are used as skin adhesives, alarge amount of absorbing particles are often added to handle themoisture.

The addition of particles in large amounts results in a relatively hardadhesive material, which has reduced tack and weak durability and oftenleads to skin stripping. To avoid this kind of skin damage, it can be anadvantage to use a permeable adhesive material that can handle themoisture developed at the skin surface. Hereby no or a low amount ofhydrocolloids needs to be added.

It has been found that pressure sensitive adhesives based on polarethylene copolymers and polar oil or a combination of polar oilsprovides an excellent skin adhesive.

These adhesives also have a very high moisture vapour transmission rate,which makes them breathable and very skin friendly. The high moisturetransmission of these adhesives is a particular advantage where amedical device has to be worn on the skin for a long time, e.g. days.

It has surprisingly been found, that the adhesives according to theinvention provide softness, flexibility, safety and comfort in wear, alow toxicity compared with acrylic adhesives and a good moisturetransmission compared to silicon adhesives.

SUMMARY OF THE INVENTION

Polymers that may be used in the practice of the invention willgenerally be copolymers of ethylene and a polar monomer. The copolymerstypically comprise less than about 70% ethylene, have water vapourtransmission of more than 50 g/m²/day and a melt flow index of less than2 g/10 min (190° C./21.1N). The melt flow index can be measured by themethods given in ISO 1133 and ASTM D1238. Examples of such polymers arecopolymers of ethylene and vinyl acetate and copolymers of ethylene andbutyl acrylate. Particularly preferred is ethylene and vinyl acetatecopolymers with more than about 40% (w/w) vinyl acetate, a melt flowindex of less than 2 g/10 min (190° C./21.1N), and a water vapourtransmission of more than 50 g/m²/day for a 150 μm sheet when measuredaccording to MVTR Test Method.

Polar oils, which may be used in the invention, will generally be thosethat have good solubility in the polar domains of the polymer, i.e.provide softness without sacrificing too much tensile strength of thepolymer. Oils that can support good water vapour permeability arepreferred. Examples of such oils are vegetable and animal oils andderivatives thereof. Preferred polar oils are esters, ethers and glycolsand particularly preferred is Poly Propylene Oxide, e.g.alpha-butoxy-polyoxypropylene.

DETAILED DESCRIPTION OF THE INVENTION

It has now been discovered that hot melt adhesives with aggressive tackand peel as well as good water vapour permeability can be obtained inusing polar ethylene copolymers, when the polymer with a low melt flowindex is formulated with a suitable polar oil and optionally otheringredients.

The adhesives of the invention exhibit unique features that make themuseful for a variety of applications. Features such as good adhesion toskin, high water vapour transmission rate and resistance to radiationsterilisation. These features make the adhesives of the invention wellsuited adhesives for many applications and particularly well suited formedical applications such as faecal management devices, wound careappliances, and incontinence devices.

The breathable adhesives of the invention may be used for fixationapplications, e.g. as adhesives for medical tapes, band aids andfixation of pads, foams or needles, providing good adhesion, highbreathability and sterilisation tolerance.

Adhesives of the invention may be formulated as traditional hydrocolloidcontaining adhesives providing improved moisture handling properties andimproved sterilisation tolerance.

The high moisture vapour transmission rate of the adhesives of theinvention makes them very suitable for laminated device constructionswith more than one adhesive layer. In example devices, where anon-absorbing substrate contact layer is combined with an absorbing bulkadhesive layer combining tack and durability with good absorption.

In one embodiment of the present invention, a pressure sensitive, hotmelt processable adhesive composition comprising a polar plasticisingoil or a combination of polar plasticising oils in the content of above10% (w/w) of the final adhesive, and at least one polar polyethylenecopolymer, wherein the content of the polyethylene copolymer is 10-50%(w/w) of the final adhesive, the polyethylene copolymer has a melt flowindex below 2 g/10 min (190° C./21.1N).

In one embodiment of the present invention, a pressure sensitive, hotmelt processable adhesive composition is produced by mixing a polarplasticising oil or a combination of polar plasticising oils in thecontent of above 10% (w/w) of the final adhesive, and at least one polarpolyethylene copolymer, wherein the content of the polyethylenecopolymer is 10-50% (w/w) of the final adhesive, the polyethylenecopolymer has a melt flow index below 2 g/10 min (190° C./21.1N).

In an embodiment of the invention, the final adhesive in continuous formexhibiting moisture vapour transmission rate of at least 100 g/m²/dayfor a 150 μm adhesive sheet when measured according to MVTR Test Method.

The primary polymers used in the adhesive composition are ethylenecopolymers. The copolymer should contain a considerable amount of apolar component to get high water permeability. Preferably, the ethyleneparts of the copolymer can form crystalline areas that ensure thecohesive strength of the adhesive.

In one embodiment of the invention, the polar polyethylene copolymer isselected from the group consisting of ethylene vinyl acetate, ethylenevinyl acetate carbon monoxide, ethylene butyl acetate, ethylene vinylalcohol, ethylene butyl acrylate, ethylene butyl acrylate carbonmonoxide, and combinations thereof.

The polar polyethylene copolymer is preferably ethylene vinyl acetate.

By polar polymers is meant polymers with water transmission above 50g/m²/day for a 150 μm film when measured according to MVTR Test Method.

One object of this invention is to provide water permeable adhesive thatis an adhesive, which can be hot-melt processed and which at normal useconditions can be removed without leaving significant residues.

In an embodiment of the invention the ethylene vinyl acetate has acontent of at least 40% (w/w) vinyl acetate preferably with 40-80% (w/w)vinyl acetate.

The adhesive composition should fulfill the Dahlquist's criterion.Preferably, the modulus should be below 100 000 Pa, and for very soft,skin friendly and comfortable adhesive the modulus (G′) could be as lowas 1-30 kPa measured by DMA at 32° C. and 1 Hz.

It is of great importance, that the adhesive is as soft as possible toensure a skin friendly material that is comfortable to wear. To get asoft material, the polymer content should be as low as possible. Themaximum polymer content of the polar polyethylene copolymer should notexceed 50% (w/w) of the final adhesive.

Preferably, the polar polyethylene copolymers used in the adhesiveshould have a molecular structure at a level that results in a melt flowindex (MFI) below 2 g/10 min (190° C./21.1N). The melt flow index can bemeasured by the methods given in ISO 1133 and ASTM D1238.

The advantage of using a polymer with high molecular weight and low MFIis that the high molecular weight polymer can ensure a sufficient highcohesive strength to the adhesive.

By the content of the final adhesive is meant the percentage in weightof the ingredient in relation to the total weight of the ingredientsused in the adhesive composition.

In an embodiment of the invention, the content of the polar polyethylenecopolymer is 10-45% (w/w) of the final adhesive preferably 15-30%.

In another embodiment of the invention, the polar polyethylene copolymerhas a molecular weight above 250000 g/mol.

In one embodiment of the present invention, the adhesive compositioncomprising a polar plasticising oil or a combination of polarplasticising oils in the content of 20-70% (w/w) of the final adhesivepreferably 40-65%.

Polar oils, which may be used in the invention, will generally be thosethat have good solubility in the polar domains of the polymer, i.e.provide softness without sacrificing too much tensile strength of thepolymer. Oils that can support good water vapour permeability arepreferred, a 50:50 mix of polymer and oil should have a moisture vapourtransmission rate of at least 100 g/m²/day. Examples of such oils arevegetable and animal oils and derivatives thereof. Preferred polar oilsare esters, ethers and glycols and particularly preferred is PolyPropylene Oxide, e.g. alpha-butoxy-polyoxypropylene.

The adhesive should preferable contain about or more than 50%plasticising oil to get the optimal softness and skin friendliness.

In one embodiment of the present invention, the adhesive compositioncomprising a polar plasticising oil wherein the polar plasticising oilis selected from the group of liquid rosin derivatives, aromatic olefinoligomers, vegetable and animal oils and derivatives, preferable polaroils are esters, ethers and glycols and particularly preferred is polypropylene oxides such as alpha-butoxy-polyoxypropylene.

Furthermore, polypropylene oxide oil contributes to a high permeabilityof the adhesive composition.

Some of the adhesive compositions according to the invention contain aminor amount of additional polymer besides the main polymer givingcohesion. This or these additional polymers are added to give tack.These additional polymers are optional and not necessary for allpurposes.

In one embodiment of the invention, the adhesive composition furthercomprises a low molecular weight polymer, i.e. MFI>2.

The addition of a low Mw polymer to the adhesive may be an advantagewhen a lot of moist is present between the adhesive and the skin.

Preferably the total polymer content, including polar polyethylenecopolymer and additional polymers (not including oils, tackifier resinetc), should not exceed 50% (w/w) of the final adhesive.

Additional components may be added to the composition such as tackifierresin, plasticisers and wax.

In one embodiment of the invention, the adhesive composition furthercomprises a tackifying resin such as natural, modified or syntheticresins preferably polar resins such as rosins, rosin esters,hydrogenated rosins, hydrogenated rosin esters, and derivatives of suchpolar resins or pure aromatic monomer resins.

Tackifying resins can be added to control tack in the adhesives, i.e.reduce moduli and increase glass transition temperature.

The content of the tackifying resin is 0-40% (w/w) of the finaladhesive. Preferably the adhesive is substantially free of resin. Whenthe adhesive composition is containing resin the content of thetackifying resin is preferably 0.1-40% (w/w) of the final adhesive andmore preferably 10-20% (w/w) of the final adhesive.

In one embodiment of the present invention, the adhesive compositioncomprising polar plasticising oils and resin in the content of above 50%(w/w) of the final adhesive.

In one embodiment of the invention, the adhesive composition furthercomprises an additional plasticiser selected from the group of mineraloil, citrate oil, paraffin oil, phatalic acid esters, adepic acid esters(e.g. DOA), and liquid or solid resin.

In another embodiment of the invention, the adhesive composition furthercomprises a polyethylene wax.

Other ingredients may be added for auxiliary benefits. This could beantioxidants and stabilisers, fillers for rheology modification oractive components like vitamin E or ibuprofen.

In another embodiment of the invention, the adhesive composition furthercomprises other ingredients selected from the group of antioxidants,stabilisers, fillers, pigments, flow modifiers, and active ingredients.

In one preferred embodiment of the invention, the adhesive compositioncomprises polar active ingredients.

The adhesive composition according to the invention is tolerant for betasterilisation, which means that it does not significantly degrade orchange properties during beta sterilisation at a reasonable level.

In one embodiment of the invention, a beta-sterilised adhesivecomposition is based on a pressure sensitive adhesive compositionaccording to the invention.

Salts and/or hydrocolloids, as absorbing particles or polymers, may beadded to the composition to create an absorbing material.

Salt may be a water-soluble salt and can be inorganic salt or organicsalt.

According to one embodiment of the invention, the adhesive compositioncomprises water soluble inorganic salt from the group of but not limitedto NaCl, CaCl₂, K₂SO₄, NaHCO₃, Na₂CO₃, KCl, NaBr, NaI, K₁, NH₄Cl, AlCl₃and mixtures thereof, preferably NaCl.

According to another embodiment of the invention, the adhesivecomposition comprises water soluble organic salt from the group of butnot limited to CH₃COONa, CH₃COOK, COONa, COOK and mixtures thereof.

The adhesive can be used without particles in devices, which rely ontransmission rather than absorption.

As with traditional HC adhesives, most liquid absorbing polymericparticles can be used, including microcolloids. A special advantage witha permeable adhesive is that a surface film will not block absorptioncompletely.

More particularly, the hydrocolloids may be guar gum, locust bean gum(LBG), pectin, alginates, potato starch, gelatine, xanthan, gum karaya;cellulose derivatives (e.g. salts of carboxymethylcellulose such assodiumcarboxymethylcellulose, methylcellulose, hydroxyethyl celluloseand hydroxypropylmethylcellulose), sodium starch glycolate,polyvinylalcohol and/or polyethylene glycol.

Microcolloid particles are well known in the art e.g. from InternationalPatent Application No. WO 02/066087, which discloses adhesivecompositions comprising microcolloid particles. The microcolloidparticles may have a particle size of less than 20 microns.

The invention also relates to medical devices comprising a pressuresensitive adhesive composition as described above.

The medical device comprising an adhesive composition according to theinvention may be an ostomy appliance, a dressing (including wounddressings), a wound drainage bandage, a skin protective bandage, adevice for collecting urine, an orthose or a prosthese, e.g. a breastprothesis, a faecal management device, and electronic device such as ameasuring instrument or a power source, such as a battery.

The medical device may also be a tape (e.g an elastic tape or film), ora dressing or a bandage, for securing a medical device, or a part of themedical device to the skin, or for sealing around a medical deviceattached to the skin.

The medical device may in its simplest construction be an adhesiveconstruction comprising a layer of the pressure sensitive adhesivecomposition according to the invention and a backing layer.

The backing layer is suitably elastic (has a low modulus), enabling theadhesive construction to conform to the skin movement and providecomfort when using it.

In a preferred embodiment of the invention, the backing material has astructured surface to improve the adhesion between adhesive and thebacking material. Particularly preferred are backing materials where themolted adhesive can penetrate and create mechanical interlocking with,for example Non Woven and non-woven film laminates.

The thickness of the backing layer used according to the invention isdependent on the type of backing used. For polymer films, such aspolyurethane films, the overall thickness may be between 10 to 100 μm,preferably between 10 to 50 μm, most preferred about 30 μm.

In one embodiment of the invention, the backing layer is non-vapourpermeable.

In another embodiment of the invention, the backing layer is watervapour permeable and has a moisture vapour transmission rate above 500g/m²/24 h. In this case the adhesive construction of the invention mayprovide a good moisture transmission rate and is able to transport alarge quantity of moisture through the construction and away from theskin. Both the chemical composition and physical construction of theadhesive layer and the chemical and physical construction of the backinglayer affect the water vapour permeability. With regard to the physicalconstruction, the backing layer may be continuous (no holes,perforations, indentations, no added particles or fibers affecting thewater vapour permeability) or discontinuous (it has holes, perforations,indentations, added particles or fibers affecting the water vaporpermeability).

The moisture vapour transmission rate of the backing layer is suitablyabove 500 g/m²/24 h, most preferably above 1000 g/m²/24 h, even morepreferred above 3000 and most preferred above 10.000.

In another embodiment of the invention, a layered adhesive constructcomprising a backing layer and at least one layer of a pressuresensitive adhesive composition according to the invention.

The adhesive according to the invention may be foamed into foamedadhesive in a number of ways, either chemically or mechanically.

Chemical blowing agents or other materials added to the adhesive formulaitself may generate gas bubbles by a variety of mechanisms. Thesemechanisms include but are not limited to chemical reaction, physicalchanges, thermal decomposition or chemical degradation, leaching of adispersed phase, volatilisation of low boiling materials or by acombination of these methods.

Any of the commercially known chemical blowing agents may be used. Thechemical blowing agents is suitably non-toxic, skin friendly, andenvironmentally safe, both before and after decomposition.

The amount of chemical blowing agent to be added to the adhesive mixturemay range from about 0.01% up to about 90% by weight, with a practicalrange including about 1% up to about 20% by weight. The amount of gas tobe added may be determined by measuring the amount of gas generated froma candidate mixture and calculating the amount of foaming required forthe final product, tempered by experience of the amount of gas lost toatmosphere during the foaming process.

Another method for creating a foamed adhesive of the invention is amethod where a mechanical process is used to add a physical blowingagent, similar to whipping the adhesive mass into froth, thus creating afoamed structure. Many processes are possible including processesinvolving incorporation of air, nitrogen, carbon dioxide, or other gasesor low boiling point volatile liquids during the manufacturing processfor the adhesive.

For some medical devices it is important that the adhesive has highmoisture vapour transmission rate, whereas the water absorption capacityis less important. This is the case with very thin dressings (e.g. foruse on the face), wound dressings having an absorbent element or padincorporated into the dressing, skin protective dressings used over skinwhere there are no cuts or wounds, etc.

For these uses, the adhesive preferably has a high moisture vapourtransmission rate but does not necessary need to have a high absorptioncapacity. A certain water absorption capacity may function as a bufferin case of severe perspiration. However, a high water absorptioncapacity also makes the water resistance of the adhesive lower, e.g.during washing or showering. Absorption of exudates from a wound may behandled by a separate absorbent element and the moisture vapourtransmission rate of the adhesive is therefore in many cases moreimportant than water absorption capacity.

According to one embodiment, the invention therefore relates to adressing such as very thin dressings for use on the face, wounddressings having an absorbent element or a pad incorporated into thedressing, or skin protective dressings used over skin where there are nocuts or wounds.

According to a further embodiment, the invention relates to a medicaldevice as above, e.g. a thin adhesive dressing, wherein the thickness ofthe adhesive layer is between 50 and 250 μm where it is thickest. Theadhesive layer may thus have varying thickens or it may have a uniformthickness selected from values between 50 and 250 μm.

A dressing of the invention may in a preferred embodiment comprise anabsorbing pad for the uptake of body fluids, especially wound exudates,so as to enable the wound dressing to keep a constant moist environmentover the wound site, and at the same time avoiding maceration of theskin surrounding the wound.

According to still another embodiment of the invention, the medicaldevice is a wound dressing as described above comprising an absorbentpad and where the thickness of the adhesive layer is between 50 and 300μm where it is thickest. The adhesive layer may thus have varyingthickens or it may have a uniform thickness selected from values between50 and 300 μm.

An absorbent pad may be situated at the surface of the adhesive layerfor contacting the wound or skin or between the adhesive layer and abacking.

A suitable foam material for use as a pad material for a dressing of theinvention is e.g. a polyethylene foam, a polyurethane foam, apolyalkylene oxide and/or polyalkylene oxide siloxane foam.

An absorbent pad may comprise hydrocolloids, super absorbents, or foamsor natural or synthetic materials which have extensive capacity toabsorb body fluids, especially wound exudates. The absorbent pad maycomprise an exudate distributing material. This renders it possible toutilise the areas of absorbent layer not being located right above thewound as well as the wetted surface of the absorbent layer will beenlarged and thus the evaporation through the backing layer will beenhanced.

The absorbent pad may be in the form of one or more layers, e.g. amultilayer, comprising layers of different absorption properties inorder to optimise the absorption capacity of the absorbent layer. Theabsorbent pad may be in the form of a matrix structure, e.g. withincorporated particles. When the absorbent pad comprises a materialcapable of distributing the absorbed exudate, full utilisation of theabsorption capacity in the dressing may be obtained.

The absorbent pad may comprise particles or fibres of any absorbentmaterial known per se being suitable for use in wound care devices, e.g.polyacrylate, CMC, cellulose or derivatives thereof, gums, foam oralginate. A dressing of the invention may be produced in a manner knownper se for applying an adhesive material onto a backing, e.g. laminatingor dye casting or spreading the adhesive to a part of or the whole ofone surface of the backing.

A dressing of the invention is optionally covered partly or fully by oneor more release liners, or cover films to be removed before or duringapplication. A protective cover or release liner may for instance besiliconised paper. It does not need to have the same contour as thedressing, and a number of dressings may be attached to a larger sheet ofprotective cover. The release liner may be of any material known to beuseful as a release liner for medical devices.

The protective cover is not present during the use of the dressing ofthe invention and is therefore not an essential part of the invention.Furthermore, the dressing of the invention may comprise one or more “nontouch” grip (s) known per se for applying the dressing to the skinwithout touching the adhesive layer. Such a non-touch grip is notpresent after application of the dressing. For larger dressings it issuitable to have 2 or 3 or even 4 “non-touch” grips.

Dressings comprising an absorbing pad or element for the uptake of bodyfluids, especially wound exudates, so as to enable the wound dressing tokeep a constant moist environment over the wound site, are described inWO 02/05737, U.S. Pat. No. 5,086,764, EP 641 553, WO 91/01706 and EP 236104. The adhesive according to the present invention may replace theadhesive comprised in any of these known dressings.

Flexibility in the adhesive part of a medical device is often achievedby device design, such as bevelling or patterning in the adhesive.

A dressing or adhesive sheet of the invention may have bevelled edges inorder to reduce the risk of “rolling-up” the edge of the dressingreducing the wear-time. A bevelling may be carried out discontinuouslyor continuously in a manner known per se e.g. as disclosed in EP PatentNo. 0 264 299 or U.S. Pat. No. 5,133,821

In another aspect, the invention relates to a wafer for an ostomyappliance comprising an adhesive construction as described above.

An ostomy appliance of the invention may be in the form of a waferforming part of a two-piece appliance or in the form of a one-pieceappliance comprising a collecting bag for collecting the materialemerging from the stoma. A separate collecting bag may be attached tothe wafer by any manner known per se, e.g. through mechanical couplingusing a coupling ring or through use of adhesive flanges.

A wafer for an ostomy appliance of the invention also typicallycomprises a water vapour permeable and water impervious reinforcementmaterial and a release liner as discussed above.

An ostomy appliance of the invention may be produced in a manner knownper se from materials conventionally used for the preparation of ostomyappliances.

Devices with advantageous properties may be obtained using the permeableadhesives of the invention in laminated constructions.

In one embodiment of the invention, the construction further comprisesat least one layer of a water absorbing adhesive.

Devices with very good adhesion under extreme conditions, for examplehigh moisture load from heavy sweating, may be obtained by placing alayer, preferably a thin layer, of permeable but non-absorbing adhesive(no hydrophilic fillers) of the invention between a water absorbingadhesive and the skin. This way, good adhesive power can be maintainedeven after the adhesive has absorbed a considerable amount of water.

It is a particular advantage to use the absorbing adhesive constructionsaccording to the invention in connection with ostomy appliances, becausethe adhesive can be made resistant to the aggressive fluids from thestoma, without sacrificing too much water absorption. Hence, it ispossible to make devices, which shield the skin efficiently from thecorrosive stoma fluids, and at the same time provides a healthynon-occlusive microenvironment between the adhesive and the skin.

In a further embodiment, the invention relates to prosthesis of the typeto be adhered to the skin of the user, such as a breast prosthesiscomprising an adhesive construction according to the invention.

The invention also relates to a urine collecting device comprising anadhesive construction as described above.

Urine collecting devices according to the invention may be in the formof uri-sheaths.

As mentioned above, the medical device may also be a medical tape e.g.for securing a device or a part of a device to the skin.

The medical device according to the invention may also be a measuringinstrument or a therapeutic instrument, which is attached to the skin,such as devices useful for measuring ECG (Electro CardioGraphy), EMG(Electro MyoGraphy), EEG (Electro EncephaloGraphy), blood glucose,pulse, blood pressure, pH, and oxygen.

Such measuring instruments are known in the art and they are usuallyattached to the skin by a pressure sensitive adhesive.

Examples of such devices are described in e.g. WO 03/065926, U.S. Pat.Nos. 5,054,488, 5,458,124, 6,372,951, 6,385,473 WO 99/59465 and USapplication No. 2003/0009097. An adhesive construction in accordancewith the present invention may replace the adhesive constructions usedfor attaching these devices to the skin.

In another embodiment of the invention, the adhesive is part of afaecal-collecting device, attaching a bag or another collecting deviceto the perianal skin.

In one embodiment of the invention, the medical device is abeta-sterilised medical device.

EXPERIMENTAL

Laboratory Methods

Method 1: Mixing

The adhesives were compounded in a Brabender mixer from Brabender OHG,Duisburg, Germany (contains about 60 grams) or a Herrmann Linden LK II0,5 from Linden Maschinenfabrik, Marienheiden, Germany (contains about600 grams). The chamber temperature in the mixer was approx 120° C. andthe adhesive was compounded with 50-60 rpm.

Premixtures were made from each polymer. The polymer was added to themixer and the mixer was started. When the polymer was melted and had asmooth surface, oil was added slowly in small steps, starting with a fewml, followed by increasing amounts. The following part of oil was notadded until the previous part was well mixed into the polymer.

For Levamelt/PPO adhesives, the ratio between Levamelt and PPO in thepremixture was typically approx 1:1.

The adhesive was compounded from the premixtures of polymer and oil. Thepremixture was added to the mixer together with resin and/or high MFIpolymer, if such was used in the formulation. The mixer was started, andwhen the polymer was melted and had a smooth surface, additional oil wasadded slowly in small steps, starting with a few ml, followed byincreasing amounts.

If the formulation included hydrocolloids or salt, these were added tothe adhesive and mixed for approx 15 min.

Method 2: Mechanical Degradation of Precrosslinked Levapren

In some cases, it was necessary to perform a mechanical degradation ofthe precrosslinked EVA, e.g. when Levapren VPKA 8857 was used. Thepolymer was mixed for about 10 hours in a cold Hermann Linden LK II 0,5mixer to get mechanical break down of the polymer chains. It isimportant to notice that the heating system was not turned on and themixing speed kept low, app. 20 rpm, to ensure optimal mechanical work onthe polymer. The break down of the polymer was followed by visualinspection of a thermoformed film of the treated polymer. The mechanicaltreatment was continued until only a minor amount of polymer gel-lumpsremained.

Method 3: Gamma Irradiation

Approx 1 kilo of the polymer was placed in a plastic bag. The bag waspacked and sent to the gamma irradiation supplier, e.g. BGS Beta-GammaService, Wiehl, Germany. The polymer was irradiated with the specifiedgamma dose, e.g. 30 kGy. The gamma radiation increases the molar weightof the polymer. When the polymer was returned, it was mixed with oil, toobtain premixtures as described above.

Method 4: Determination of Moisture Vapour Transmission Rate (MVTR)

MVTR was measured in grams per square meter (g/m2) over a 24 hoursperiod using an inverted cup method.

A container or cup that was water and water vapour impermeable having anopening was used. 20 ml saline water (0.9% NaCl in demineralised water)was placed in the container and the opening was sealed with the testadhesive film. The container was placed into an electrically heatedhumidity cabinet and the container or cup was placed up side down suchthat the water was in contact with the adhesive. The cabinet wasmaintained at 37° C. and 15% relative humidity (RH). The weight loss ofthe container was followed as a function of time. The weight loss wasdue to evaporation of water vapour transmitted through the adhesivefilm. This difference was used to calculate Moisture vapour transmissionrate or MVTR. MVTR was calculated as the weight loss pr time divided bythe area of the opening in the cup (g/m²/24 h). The MVTR of a materialwas a linear function of the thickness of the material. Thus, whenreporting MVTR to characterise a material, it was important to informthe thickness of the material which MVTR was reported. We used 150 μm asa reference. If thinner or thicker samples were measured, the MVTR wasreported as corresponding to a 150 μm sample. Thus a 300 μm sample witha measured MVTR of 10 g/m²/24 h was reported as having MVTR=20 g/m²/24 hfor a 150 μm sample because of the linear connection between thicknessof sample and MVTR of sample.

Finally, we noted that by using this method, we introduced an error byusing a supporting PU film. Utilising the fact, that the adhesive/filmlaminate was a system of two resistances in series eliminated the error.When the film and the adhesive were homogeneous, the transmission ratemay be expressed as:1/P(measured)=1/P(Film)+1/P(Adhesive)

Hence by knowing the film permeability and thickness of the adhesive, itwas possible to calculate the true permeability of the adhesive(P(Adhesive)) using the following expression:P(adhesive)=d(Adhesive)/150micron*1/(1/P(measured)−1/P(Film))where d(Adhesive) was the actual measured thickness of the adhesive andP(Film) was the MVTR of the film without any adhesive on and P(measured)was the actual measured MVTR.Method 5: Determination of Peel Failure Mode:

Peel failure mode was determined by peeling a suitable sample from skin.

Peel failure mode, i.e. adhesive or cohesive failure of the adhesive,was visually observed. Cohesive failure was unwanted, as adhesives withcohesive failure were likely to leave residues on the substrate whenremoved.

The test samples were prepared by thermoforming an approximately 200micron adhesive film between two release liners. Said adhesive film wastransfer coated onto an 80 gsm elastic non-woven from BBA Fiberweb(Dreamex, CS9540002, 80 gsm), and heat treated at 100° C. for about 5minutes to thoroughly bond the adhesive to the NW. 1 cm wide testspecimens were cut along the low module axis of the non-woven.

The test specimens were applied to the underside of the forearm and leftfor about 2 hours before they were peeled. The results were reported asAdhesive or Cohesive peel failure mode.

Method 6: DMA and Determination of G′ and Tan(δ)

The parameters G′ and tan(δ) were measured as follows: The adhesiveswere pressed into a plate of 1 mm thickness. A round sample of 25 mm indiameter was cut out and placed in a RheoStress RS600 rheometer fromThermo Electron. The geometry applied was parallel plates 25 mm and thedeformation was fixed at 1% to ensure that measurements were in thelinear regime. The measurements were carried out at 32° C.

Materials

Name Chemistry Supplier Levamelt Copolymers of ethylene and Lanxess,Germany vinyl acetate (VA). Evatane Copolymers of ethylene and ATOFINAvinyl acetate (VA). Chemicals Inc. Polyglycol Poly(propylene oxide) oilClariant, Germany B01/120 (PPO) (Mw = 2000) Pine Crystal, KE311Hydrogenated rosin ester Arakawa, Japan resin Suprasel, Fine particulateSodium Akzo Nobel Salt NaCl Chloride powder A/S Aquasorb A800Crosslinked CMC particles Hercules Bioflex 130 PU film, 25 micron ScapaDreamex PU/PE NW, 80 gsm BBA Fiberweb CS9540002Results

EXAMPLE 1 Permeability Of Different EVA Polymers

Film was prepared by thermoforming the neat polymer in a warm press atabout 100° C., and MVTR was measured (Method 4):

MVTR MVTR EVA polymer permeability measured 150 micron Support g/m²/24g/m²/24 Sample name Film hours hours LDPE, 160 micron non 15 16 Evatane28-25, 270my 65 117 Levamelt 400 (40% VA, non 47 110 290 micron)Levamelt 450 (45% VA, non 94 181 290 micron) Levamelt 500 (50% VA, non111 201 270 micron) Levamelt VPKA 8857 (50% VA, non 125 280 340 micron)Levamelt 700 (70% VA, non 118 240 330 micron)

EVA polymers with low VA have a low MVTR and hence make less suitablebase polymers for a permeable hot-melt processable pressure sensitiveadhesive. In addition only fairly hydrophobic oil and resins arecompatible with low VA EVA, and hence the resulting adhesives will havea low permeability.

EXAMPLE 2 Peel and Permeability of Different Adhesives Based on EvaPolymers With Different MFI Index

The following adhesives were hot-melt compounded according to methods 1,2 and 3. Peel failure mode was determined according to method 5:

STR041.1 STR040.7 STR041.2 STR040.8 STR041.3 STR037.4 Levamelt 700 45.0MFI = 4 Levamelt 700, 30KGy, 45.0 MFI < 2 Levamelt 500 28.6 MFI = 3Levamelt 500, 50 KGy, 28.6 (Levapren VPKA 8857) MFI < 2 Levamelt 45025.0 MFI = 5 Levamelt 450, 30 KGy, 25.0 MFI < 2 Levamelt VP KA 8896 19.019.0 10.0 10.0 (MFI >> 2) PolyGlycol 55.0 55.0 52.4 52.4 65.0 65.0 PPOB01/120 Peel failure mode Cohesive Adhesive Cohesive Adhesive CohesiveAdhesive

The example illustrates that adhesives made with polymers with MFI<2have a much improved ratio between adhesiveness and cohesive strength,i.e. they leave little or no residues on the substrate when peeled.Adhesives made only with polymers with MFI>2 have a tendency to failcohesively and hence leave an unacceptable amount of residues whenremoved.

EXAMPLE 3 Permeability of Adhesives with High and Low Resin Content

Four adhesives were compounded according to the methods 1, 2 and 3

STR040.7 STR043.1 STR043.2 STR043.3 Levamelt 700, 30 KGy 45.0 45.0 45.045.0 Polyglycol PPO 55.0 45.0 27.5 B01/120 Pine Crystal KE-311 55.0 10.027.5

The adhesives were thermoformed to about 250 microns between a PU film(Bioflex 130) and a release liner. The transmission rate was measuredaccording to Method 4:

Resin Transmission % g/m²/day STR040.07 0 1127 STR043.02 10 703STR043.03 32.5 350 STR043.01 55 37

The example shows that an adhesive according to the invention maycontain some tackifier resin, but that they generally reducetransmission. Levels below about 50% seem to be acceptable, butpreferably the level should be even lower.

EXAMPLE 4 Adhesives According to the Invention

The table beneath shows examples of adhesive compositions preparedaccording to the invention and methods 1, 2 and 3.

Sample number STR039.4 STR039.11 STR039.L9 STR034.25 STR040.7 STR005.42Levamelt VPKA 25%   27% Laminate 25%  30% 8857 of MFI < 2 Film +Levamelt 700, 800 45% 30KGy Gamma micron MFI < 2 STR039.4 + Levamelt 700— — 100 5% — MFI = 4 micron Levamelt VP KA 20% 13.5% STR039.11 5% — 8896MFI >> 2 PolyGlycol 55% 49.5% 65%  55% 50% B01/120 Pine Crystal, KE- — —— 20% 311 Suprasel, NaCl —   10% — — Peel failure mode adhesive adhesiveadhesive adhesive adhesive adhesive Transmission 820 g/m2/ 2990 g/m2/ nm1210 g/m2/ 1130 g/m2/ 490 g/m2/ (150 micron) day day day day day Module,21000 Pa 40400 Pa nm 13800 Pa 30500 Pa 21400 Pa G′, 1 Hz

It can be noted that key performance properties, such as peel failuremode, transmission and moduli, all comply well with the criteria for anadhesive according to the invention.

EXAMPLE 5 Sterilisation Tolerance

Materials:

Name Chemistry Supplier Levamelt Copolymers of ethylene and Lanxess,vinyl acetate (VA). Grades with Germany VA content between 40% and 80%B01/120 (PPO) Poly(propylene oxide) oil Clariant, Germany (Mw = 2000)Pine Crystal Hydrogenated rosin ester Arakawa, Japan KE311 Citrofol BIIAcetyl tributyl citrate Jundbunzlauer, Germany Blanosecarboxy-methyl-cellulose Aqualon/Hercules (CMC) hydrocolloid AquasorbA800 x-linked CMC hydrocolloid Aqualon/HerculesAdhesives:

STR020.03 STR025.F03 STR025.14 STR025.15 Levamelt 400 16.9 19.4 Levamelt700 20.0 9.7 PPO B01/120 27.0 29.1 KE311 resin 36.0 38.8 Citrofol BII3.0 Blanose 20.0 Aquasorb A800 20.0 STR025.F03 80.0 80.0

The adhesives were produced according to method 1, thermoformed into 1mm sheets which were sent for Beta-ray sterilisation at a dose of 0,17.5 KGy & 2×17.5 KGy. DMA was performed according to method 6.

Results:

G′ (Pa) G′ (Pa) tan(δ) at tan(δ) at at Dose 1 Hz & at 1 Hz 0.01 Hz 0.01Hz Sample No. (*17.5kGy) 32° C. & 32° C. & 32° C. & 32° C. STR020.03 0 38900 0.59 5700 0.83 1* 37700 0.60 5270 0.86 2* 33600 0.60 5160 0.78STR025.F03 0  23100 0.50 8410 0.26 1* 22900 0.50 8440 0.26 2* 24500 0.508910 0.25 STR025.14 0  43000 0.49 16600 0.26 1* 46500 0.49 18500 0.26 2*41400 0.50 15100 0.27 STR025.15 0  50000 0.51 18700 0.30 1* 43100 0.5016200 0.28 2* 42100 0.53 14600 0.30

The results show that Beta-sterilisation introduce no or only veryslight changes in mechanical properties; G′ and tan(δ) are constant,within experimental error, i.e. no significant cross linking orbreakdown of the polymer backbone is introduced.

The invention claimed is:
 1. A layered adhesive construct comprising abacking layer and at least one layer of a pressure sensitive, hot meltprocessable adhesive composition comprising polypropyleneoxide in thecontent of above 10% (w/w) of the final adhesive, and at least one polarpolyethylene copolymer, wherein the content of the polyethylenecopolymer is 10-50% (w/w) of the final adhesive, the polyethylenecopolymer has a melt flow index below 2 g/10min (190° C/21.1 N), whereinthe at least one polar polyethylene copolymer is selected from the groupconsisting of ethylene vinyl acetate, ethylene vinyl acetate carbonmonoxide, ethylene butyl acetate, ethylene vinyl alcohol, ethylene butylacrylate, ethylene butyl acrylate monoxide, and combinations thereof,provided that when the polar polyethylene copolymer is ethylene vinylacetate, the ethylene vinyl acetate has a content of at least 40% (w/w)vinyl acetate.
 2. The layered adhesive construct according to claim 1,wherein the final adhesive in continuous form exhibits a moisture vapourtransmission rate of at least 100 g/m²/day for a 150 m adhesive sheetwhen measured according to MVTR Test Method.
 3. The layered adhesiveconstruct according to claim 1, wherein the polar polyethylene copolymeris ethylene vinyl acetate.
 4. The layered adhesive construct accordingto claim 3, wherein the ethylene vinyl acetate has a content of 40-80%(w/w) vinyl acetate.
 5. The layered adhesive construct according toclaim 1, wherein the content of the polar polyethylene copolymer is10-45% (w/w) of the final adhesive.
 6. The layered adhesive constructaccording to claim 1, wherein the polar polyethylene copolymer has amolecular weight of above 250,000 g/mol.
 7. The layered adhesiveconstruct according to claim 1, wherein the composition further includesan additional plasticizer selected from the group consisting of ofliquid rosin derivatives, aromatic olefin oligomers, vegetable andanimal oils and derivatives, esters, ethers and glycols, andalpha-butoxy-polyoxypropylene.
 8. The layered adhesive constructaccording to claim 7, wherein the content of the polypropylene oxideplus the additional plasticizer is 20-70% (w/w) of the final adhesive.9. The layered adhesive construct according to claim 1, wherein thecomposition further comprises a polymer with MFI >2(190° C/21.1N). 10.The layered adhesive construct according to claim 1, wherein thecomposition further comprises a tackifying resin.
 11. The layeredadhesive construct according to claim 10, wherein the content of thetackifying resin is 0.1-40% (w/w) of the final adhesive.
 12. The layeredadhesive construct according to claim 1, wherein the composition furthercomprises an additional plasticiser selected from the group consistingof mineral oil, citrate oil, paraffin oil, phatalic acid esters, adepicacid esters, and liquid and solid resin.
 13. The layered adhesiveconstruct according to claim 1, wherein the composition furthercomprises a polyethylene wax.
 14. The layered adhesive constructaccording to claim 1, wherein the composition further comprises otheringredients selected from the group consisting of antioxidants,stabilisers, fillers, pigments, flow modifiers, and active ingredients.15. The layered adhesive construct according to claim 14, wherein theother ingredients are polar active ingredients.
 16. The layered adhesiveconstruct according to claim 1, wherein the composition furthercomprises absorbing particles.
 17. The layered adhesive constructaccording to claim 16, wherein the absorbing particles comprisehydrocolloid and the amount of hydrocolloid is below 50% w/w of thetotal composition.
 18. The layered adhesive construct according to claim1, wherein the composition further comprises a salt.
 19. The layeredadhesive construct according to claim 18, wherein the salt is a watersoluble inorganic salt selected from the group consisting of NaCl,CaCl₂, K₂SO₄ , NaHC0₃, Na₂CO₃, KCl, NaBr, NaI, KI, NH₄Cl, AlCl₃, andmixtures thereof.
 20. The layered adhesive construct according to claim18, wherein the salt is a water soluble organic salt selected from thegroup consisting of CH₃COONa, CH₃COOK, HCOONa, HCOOK and mixturesthereof.
 21. A beta-sterilised layered adhesive construct according toclaim
 1. 22. The layered adhesive construct according to claim 1,wherein the construct further comprises at least one layer of a waterabsorbing adhesive.
 23. The layered adhesive construct according toclaim 22, wherein the layer of a pressure sensitive adhesive compositionis between said layer of a water absorbing adhesive and the skin.
 24. Amedical device comprising (a) a pressure sensitive hot melt processibleadhesive composition containing polypropyleneoxide in the content ofabove 10% (w/w) of the final adhesive, and at least one polarpolyethylene copolymer, wherein the content of the polyethylenecopolymer is 10-50% (w/w) of the final adhesive, the polyethylenecopolymer has a melt flow index below 2 g/10min (190° C/21.1N), whereinthe at least one polar polyethylene copolymer is selected from the groupconsisting of ethylene vinyl acetate, ethylene vinyl acetate carbonmonoxide, ethylene butyl acetate, ethylene vinyl alcohol, ethylene butylacrylate, ethylene butyl acrylate monoxide, and combinations thereof,and (b) a backing layer.
 25. The medical device according to claim 24,wherein the backing layer is non-vapour permeable.
 26. The medicaldevice according to claim 24, wherein the backing layer is water vapourpermeable and has a moisture vapour transmission rate above 500g/m²/24h.
 27. The medical device according to claim 24, wherein themedical device is a dressing, an ostomy appliance, a prosthesis, abreast prosthesis, a urine collecting device, a faecal managementdevice, a measuring instrument or a therapeutic instrument, a medicaltape, or a dressing or bandage for sealing around a medical device onthe skin.
 28. The medical device according to claim 24, wherein themedical device is a beta-sterilised medical device.
 29. The layeredadhesive construct according to claim 1, wherein the content of thepolar polyethylene copolymer is 15-30% (w/w) of the final adhesive. 30.The layered adhesive construct according to claim 7, wherein the contentof the polypropylene oxide plus the additional plasticizer is 40-60%(w/w) of the final adhesive.
 31. The layered adhesive constructaccording to claim 10, wherein the tackifying resin is selected from thegroup consisting of natural, modified and synthetic resins, polarresins, rosin esters and derivatives thereof, and pure aromatic monomerresins.
 32. The layered adhesive construct according to claim 10,wherein the content of the tackifying resin is 10-20% (w/w) of the finaladhesive.